Friday 31 October 2008
Thursday 30 October 2008
kripke's modal argument for (substance?) dualism
Im going to outline Saul Kripke's modal argument for a dualism of the mind and body. I've just started reading his famous book Naming & Necessity (based on a series of lectures he gave in the 1970's) for university, so perhaps all of the details I'm about to relay aren't one hundred percent accurate, but this is the general gist of what I think he's getting at.
His argument comes at the end of the book and it relies on the theory of names he'd already developed earlier on in the first chapter which, due to space, im not going to go into in any great detail. Essentially before Kripke (Frege & Russell being the two most prominent proponents) names were thought to be synonymous with a (cluster of) descriptions - for example 'Aristotle' would have been synonymous with 'teacher of Alexander the Great, student of Plato, writer of the Metaphysics etc.'. If this is the case then names are 'non-rigid' designators (to use Kripke's terminology) - the name 'Aristotle' thus considered in another possible world may not apply to the man who it actually designates in this the actual world, because in some other world Aristotle may have done none of the things he is famous for doing in this world. In some other possible world 'Aristotle' may pick out a totally different person who does all of the things Aristotle in this world is known for doing. For Kripke, however, proper names like 'Aristotle' turn out to be 'rigid' designators - they pick out the same person in all possible worlds, which means they aren't shorthand for a cluster of properties after all. Without going over his arguments as to why (I'll perhaps save them for a later blog), it also turns out that not only are proper names rigid designators, but also 'natural kind' terms are rigid designators - terms like 'gold', 'water', 'tiger' etc. pick out the same kind of thing in every world in which that thing exists.
The upshot of all this is that theoretical identity statements become necessary (they hold across all possible worlds in which those entities exist). So, for example, if 'lightning' and 'electrical discharge' pick out the same thing in this world (i.e. lightning just is an electrical discharge) then, necessarily, they pick out the same thing in every possible world - there cannot be a possible world in which lightning isn't an electrical discharge. Maybe in another world there is something like lightning which isn't an electrical discharge: something that has similair effects and a similair look to lightning, yet it just wouldn't be lightning. Why? Because, again, if the terms 'lightning' and 'electrical discharge' are 'rigid-designators', picking out the same thing in all worlds, and they are identical in at least one world then they must be identical in every world.
So how does all this relate to the contemporary mind-body problem? Well, the mind-body identity thesis is a form of materialism that holds that mental sensations just are physical brain processes. For example pain just literally is a c-fiber firing in the brain somewhere - it isn't anything over and above the physical process, it is identical with it in the same way lightning and electrical discharge or water and h20 are the same entity. So if the natural kind terms 'pain' and 'c-fiber' pick out the same thing in this world then necessarily pain must be a c-fiber firing in every possible world there is pain. This seems a strong claim, but the identity theorist may be willing to say this is just how it is. Kripke's argument against this conclusion is simply that we can conceive of a world in which there was a c-fiber firing without the corresponding feeling of pain (and vice versa, a pain with no c-fiber firing). The identity theorist may wish to explain this away by appealing to something like heat being identical to molecular motion. In some other world we can imagine the feeling of heat that we have now identified with molecular motion not existing - perhaps we have evolved in such a way that we can't feel this heat 'qualia' (sensation). In this case, though, it would appear we could still detect heat through detecting molecular motion. So the actual qualitative feeling of heat becomes a 'non-rigid' designator we use to pick out the phenomena of heat in this world - it is an 'accidental' property of heat (not necessary/essential to its nature of being heat), while its being molecular motion is essential to it. This means that if there were no molecular motion then there would be no heat, but the converse doesn't hold - if we (or any other observer) cannot experience the qualitative feel of heat there still could be heat if there was the required molecular motion occuring in that world. Kripke, however, thinks we cannot do a similair thing with pain and c-fiber firings. The felt quality of pain isn't something accidental to its being pain in the same way the felt quality of heat is accidental to it's being heat - if there is no felt quality of pain, yet a c-fiber still fires, we are compelled to say that it's not pain. In essence what is being said is that when we think of pain we don't think of a c-fiber firing as being something essential to it while its raw felt quality is something accidental to it's nature in the same way we see molecular motion being essential to heat while its felt quality is accidental. In that world where there is a c-fiber firing with no corresponding pain qualia and molecular motion with no corresponding heat qualia it appears we would be forced to draw two different conclusions: firstly that there is no pain in that world and secondly that there is still heat there.
Because the identity theorist cannot account for the above the identity theory of the mind and body is false and the mind really is distinct from anything physical. The identity theorist may reply that despite appearances it really isn't possible that a pain could be anything other than a c-fiber firing - which brings us into an area explored by the likes of David Chalmers and Stephen Yablo on whether sheer conceivability entails possibility (for a future post methinks).
Simple eh?
His argument comes at the end of the book and it relies on the theory of names he'd already developed earlier on in the first chapter which, due to space, im not going to go into in any great detail. Essentially before Kripke (Frege & Russell being the two most prominent proponents) names were thought to be synonymous with a (cluster of) descriptions - for example 'Aristotle' would have been synonymous with 'teacher of Alexander the Great, student of Plato, writer of the Metaphysics etc.'. If this is the case then names are 'non-rigid' designators (to use Kripke's terminology) - the name 'Aristotle' thus considered in another possible world may not apply to the man who it actually designates in this the actual world, because in some other world Aristotle may have done none of the things he is famous for doing in this world. In some other possible world 'Aristotle' may pick out a totally different person who does all of the things Aristotle in this world is known for doing. For Kripke, however, proper names like 'Aristotle' turn out to be 'rigid' designators - they pick out the same person in all possible worlds, which means they aren't shorthand for a cluster of properties after all. Without going over his arguments as to why (I'll perhaps save them for a later blog), it also turns out that not only are proper names rigid designators, but also 'natural kind' terms are rigid designators - terms like 'gold', 'water', 'tiger' etc. pick out the same kind of thing in every world in which that thing exists.
The upshot of all this is that theoretical identity statements become necessary (they hold across all possible worlds in which those entities exist). So, for example, if 'lightning' and 'electrical discharge' pick out the same thing in this world (i.e. lightning just is an electrical discharge) then, necessarily, they pick out the same thing in every possible world - there cannot be a possible world in which lightning isn't an electrical discharge. Maybe in another world there is something like lightning which isn't an electrical discharge: something that has similair effects and a similair look to lightning, yet it just wouldn't be lightning. Why? Because, again, if the terms 'lightning' and 'electrical discharge' are 'rigid-designators', picking out the same thing in all worlds, and they are identical in at least one world then they must be identical in every world.
So how does all this relate to the contemporary mind-body problem? Well, the mind-body identity thesis is a form of materialism that holds that mental sensations just are physical brain processes. For example pain just literally is a c-fiber firing in the brain somewhere - it isn't anything over and above the physical process, it is identical with it in the same way lightning and electrical discharge or water and h20 are the same entity. So if the natural kind terms 'pain' and 'c-fiber' pick out the same thing in this world then necessarily pain must be a c-fiber firing in every possible world there is pain. This seems a strong claim, but the identity theorist may be willing to say this is just how it is. Kripke's argument against this conclusion is simply that we can conceive of a world in which there was a c-fiber firing without the corresponding feeling of pain (and vice versa, a pain with no c-fiber firing). The identity theorist may wish to explain this away by appealing to something like heat being identical to molecular motion. In some other world we can imagine the feeling of heat that we have now identified with molecular motion not existing - perhaps we have evolved in such a way that we can't feel this heat 'qualia' (sensation). In this case, though, it would appear we could still detect heat through detecting molecular motion. So the actual qualitative feeling of heat becomes a 'non-rigid' designator we use to pick out the phenomena of heat in this world - it is an 'accidental' property of heat (not necessary/essential to its nature of being heat), while its being molecular motion is essential to it. This means that if there were no molecular motion then there would be no heat, but the converse doesn't hold - if we (or any other observer) cannot experience the qualitative feel of heat there still could be heat if there was the required molecular motion occuring in that world. Kripke, however, thinks we cannot do a similair thing with pain and c-fiber firings. The felt quality of pain isn't something accidental to its being pain in the same way the felt quality of heat is accidental to it's being heat - if there is no felt quality of pain, yet a c-fiber still fires, we are compelled to say that it's not pain. In essence what is being said is that when we think of pain we don't think of a c-fiber firing as being something essential to it while its raw felt quality is something accidental to it's nature in the same way we see molecular motion being essential to heat while its felt quality is accidental. In that world where there is a c-fiber firing with no corresponding pain qualia and molecular motion with no corresponding heat qualia it appears we would be forced to draw two different conclusions: firstly that there is no pain in that world and secondly that there is still heat there.
Because the identity theorist cannot account for the above the identity theory of the mind and body is false and the mind really is distinct from anything physical. The identity theorist may reply that despite appearances it really isn't possible that a pain could be anything other than a c-fiber firing - which brings us into an area explored by the likes of David Chalmers and Stephen Yablo on whether sheer conceivability entails possibility (for a future post methinks).
Simple eh?
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